this post was submitted on 03 Feb 2024
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There's also a cost factor, traditionally automatics cost more to build, weighed more and performed slightly worse. Now, automatics are probably cheaper to build, perform better, but still cost more.
Manual will always be cheaper. Even CVTs cost more.
A Manual clutch is just a drum-brake (like object) controlled by a a reversed 3rd pedal (brake-like system engages when the pedal is released. While pushing the pedal releases the clutch, its "backwards") that allows the engine to engage with the transmission system. The gearbox has no computers, just one hydraulic line (only those associated with the 3rd pedal), and unlike a disc-brake its barely used so the drum-like system (which is even cheaper than disc brakes and lasts for 100,000+ miles easily).
The important thing is this "how do you deal with disconnecting the engine from the tires" problem. When 3rd gear is 5000 RPM for your speed, 4th gear might be 4000 RPM (depending on your gearbox of course). A Manual clutch just has the user push on the drum-brake like clutch (releasing the engine, allowing it to spin freely), then you slowly release the clutch, which causes this "brake" to slowly connect the engine with the tires (tires speed up while engine slows down).
Manual drivers get very good at this, and add engine speed / accelerate on downshifts (ex: going from 4000 RPM to 5000 RPM as you go from 4th gear to 3rd gear), you can just apply the accelerator thereby adding engine speed to assist the clutch in matching RPMs for a smooth transition.
Alternatively, manual drivers can heel-toe: apply the accelerator, brake, and clutch simultaneously. Not only is the accelerator helping push the RPM from 4000 RPM and upwards with engine... the brakes are slowing down the car bringing the "target RPM" down to 4500 RPM. So the manual driver can assist in both directions thanks to the use of all three pedals. This technique is called heel-toe because your left-leg controls the clutch, while your right-toe hits the brakes, while the right-heel hits the accelerator, and your heel/toe does different things to help match the RPMs to the Tires.
Modern automatics are:
Traditional Wet Clutch -- A Wet Clutch uses a highly viscous liquid (aka: the torque converter) that is "always slipping", no matter the conditions of the car. This means that your car is now always smooth, but the "slush" can take a while before the fluid spins-up to the speeds that matches the engine-with-the-wheels. This is the longest running technology, and someone pointed out that modern wet-clutches like ZF8 are considered quite good. So yeah, "always be disconnected" and use liquid viscosity to help match RPMs as needed.
CVTs -- unpopular due to the weird noises, but Subaru WRX has shown that its a superior system with relatively cheap manufacturing. A computer controls two hydraulic systems push upon the chain, changing the effective-gear-ratio smoothly. Early models were unreliable and broke, and some bad CVTs still exist out there. But after a few years, all CVTs are long-life and reliable. Subaru has also changed it so that modern CVTs make noises closer to traditional engines, as it turns out that the human ear of an advanced driver is constantly evaluating the engine, so our ear-training is important part of the driving experience.
Dual Clutch -- A computerized manual transmission. Computers still can't do all of the manual application that I described above. But... if you add two clutches, and switch between even-gears and odd gears. (ex: Clutch#1 controls gear 1-3-5-7, and Clutch#2 controls 2-4-6-8), then you can switch to the 2nd clutch, and then perform a computerized switch while disconnected. This cheats at the "slippage" problem, but cheating means cheaper assembly and better performance.
In all three cases, modern automatics are heavier, require more parts, more assembly. Reliability is getting better however, and as computers minimize engine slippage the transmissions are having less stress applied to them in general.
I've seen manual Fords with a little trick where it holds the revs at the speed for the next gear up, just for a second or so, to make it easier to get a perfect gear change. However, even then an automatic is far better for maintaining acceleration, and therefore more accelerating more efficiently.
Yes that's the thing, cars already have ECU's in them as a standard feature now (along with fly-by-wire in general), so the gearbox control is essentially an additional software function rather than any significant part cost. Electronic control is much less likely to burn out a clutch.
But yeah, the additional weight is what has always made autos perform worse. However in terms of cost, I do feel like automatics might come down and beat manuals eventually, particularly as traditional manual gearboxes become more rare and automatics scale up. In any case, the price a car sells for is almost completely detached from the actual cost - the price is set as high as they can get away with, not as a percentage of parts and labour. In this way, an automatic can easily be more profitable than a traditional manual.
0-60 drag races are not a common use case in daily driving. You gear shift to 2nd before making a 15mph turn. You downshift to 3rd when entering a 25mph zone. You shift to 5th (or whatever your last gear is) as you enter the highway.
Otherwise, you're rarely touching the clutch or gearbox. Sure, a 0-60 hits all gears and requires 5 shifts to be done smoothly, but that's rare.
Because I'm a human, and I can see the road... I can see that the ~15mph turn is coming up. So I can be already in 2nd gear before the turn comes up. This is useful for engine braking anyway. Then I'm in the correct gear for the turn, and out of the turn. Hitting the proper gear long-before the automatic (DCT, Wet-clutch, or CVT) would ever know about the turn.
This is not an aggressive turn for racing. Racing would likely require heel-toe, a difficult maneuver as I've described above. But for daily driving, just predicting "where the car will be" in 10 seconds and getting the gear shifts done ahead of time is really what you're doing. If you'll be in 2nd gear soon, might as well get that over with and shift slightly before its needed (5 seconds or so ahead).
That depends entirely on where you are driving. Come to a T-junction in the middle of the countryside, national speed limit, and you can easily find yourself doing that. Even on a motorway, in heavy crawling traffic, there will come a point where everyone accelerates back up to full speed. Even if you don't find yourself in these situations, changing from 3rd to 5th (or 6th) has you working through the gearbox.
Many automatics will use engine breaking also. They will downshift through the gears as you brake. And, if you want to select a gear for a specific reason, you can either put it into manual and select the gear (or if you have padals leave it in auto and downshift with those) for either a corner or to prepare for an overtake, then you can complete the maneuver and either mash all the way up or straight back into auto, then it will handle all the acceleration optimally itself. Best of both worlds.
I had one that had a sport button, this also changed the automatic shifting profile. In particular, it wouldn't shift up a gear until the next gear was above 2000RPM, where the first stage turbo comes in with diesel. So power was always on tap, rather than having to wait for a gear change from a low rev cruise.
It's not about drag racing or any other type of racing, it's about efficiency and minimising wear and tear on the equipment. Even the best drivers aren't perfect every time. An auto isn't either, but in general it's closer.
A manual is better than a bad auto, but a good auto is better than any manual.
My point is that if you're a manual driver and you don't care about the 0-60 time, then all you gotta do is slow down the clutch release so that the clutch spends... I dunno, half-a-second engaging the engine, rather than quarter-a-second or faster. Slowing down the clutch-release (erm, re-engaging the engine) smooths out the acceleration, is easy on your parts, and barely affects your acceleration times.
Its only a problem in 0-60 drag races when you're literally trying to beat everyone else off the line. But if you're just doing day-to-day relaxed driving... just take it easy. Its not like you're flooring the car anyway.
I personally always like to try to time the RPM decrease such that I can instantly lift off my leg from the pedal as quickly as possible, because I like having a little skill minigame when driving. (Matching RPMs with the speed of my car for smoother shifts, and more instant engagements). But that's really not necessary.
I mean, my gripe is more about the lack of power on the wheels. It's less about the time it takes to re-engage the clutch, more the overall time the clutch is disengaged. I want to accelerate briskly (not flooring it) and then cruise at a steady speed, to achieve maximum fuel efficiency. A good automatic handles this very well, and generally makes driving easier and more relaxed. Sure, changing gear manually and getting the clutch right can be fun, but it's objectively a worse way of doing things.
Dropping 250lbs and removing the torque converter (~2% loss alone) will do more for overall fuel efficiency for your car than anything those automatic transmissions can do.
Yeah, I get that computers + improved automatic modes of transmission control (ex: CVTs or Dual Clutch Transmissions) can improve engagement times. And the removal of the wet-clutch/slushbox of automatic transmissions grossly improves efficiency. But these units are still heavier in practice than a dumb, manual clutch.
I don't think any automatic transmission beats a manual in efficient driving yet. Because weight is king. Automatics (at least, DCTs and CVTs) are finally reaching the response times of a manual transmission by having more direct connection of accelerator pedal to the engine... but the weight issue, cost-issue are still there.
At least modern transmissions basically never brake down anymore. (CVTs, Dual Clutch, and more are all basically going to last the whole lifetime of a typical car).
Tbf the whole argument is basically moot with electric vehicles taking over.